Acid Deep Eutectic Solvent Research Articles

Optimization of cellulose extraction process from sugar beet pulp and preparation of its nanofibers with choline chloride–lactic acid deep eutectic solvents

Optimization of cellulose extraction process from sugar beet pulp and preparation of its nanofibers with choline chloride–lactic acid deep eutectic solvents

Surface Reconstruction and Low-Temperature Dyeing Performances of a Poly(Lactic Acid) Filament Pretreated with a Choline Chloride and Oxalic Acid Deep Eutectic Solvent

Surface Reconstruction and Low-Temperature Dyeing Performances of a Poly(Lactic Acid) Filament Pretreated with a Choline Chloride and Oxalic Acid Deep Eutectic Solvent

Neutron Diffraction Study of Indole Solvation in Deep Eutectic Systems of Choline Chloride, Malic Acid, and Water.

Deep eutectic systems are currently under intense investigation to replace traditional organic solvents in a range of syntheses. Here, indole in choline chloride‐malic acid deep eutectic solvent (DES) was studied as a function of water content, to identify solute interactions with the DES which affect heterocycle reactivity and selectivity, and as a proxy for biomolecule solvation. Empirical Potential Structure Refinement models of neutron diffraction data showed [Cholinium]+ cations associate strongly with the indole π‐system due to electrostatics, whereas malic acid is only weakly associated. Trace water is sequestered into the DES and does not interact strongly with indole. When water is added to the DES, it does not interact with the indole π‐system but is exclusively in‐plane with the heterocyclic rings, forming strong H‐bonds with the ‐NH group, and also weak H‐bonds and thus prominent hydrophobic hydration of the indole aromatic region, which could direct selectivity in reactions.

Deep eutectic solvent based-ferrofluid ultrasonic-assisted liquid–liquid microextraction for determination of quinolones in milk samples

In the current study, vortex assisted-liquid–liquid microextraction (VA-LLME) pretreatment method was developed based on superparamagnetic nanofluid and deep eutectic solvents for the isolation and preconcentration of quinolones in milk sample. The deep eutectic solvent-ferrofluid (DES-FF) with high extraction ability was prepared by combining DL-menthol/octanoic acid deep eutectic solvent and magnetic nanoparticles, which was mainly related to the strong interactions between extractant and analytes, such as hydrophobic interactions, hydrogen bonding attractions and electrostatic interactions. The functional group, and magnetic characteristics of the synthesized materials were characterized by using Fourier transform-infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. The use of vortex instead of dispersed solvent in LLME is simple and quick, reducing the consumption of solvent and shortening the extraction time. The parameters which affected the extraction efficiency were investigated and optimized using response surface methodology (RSM). Under the optimum conditions, linearity (r > 0.996) was in the range of 1.00–100 μg mL−1. Limit of detection (LOD) and quantification (LOQ) of two quinolones varied in 0.30–0.35 μg mL−1 and 0.80–1.0 μg mL−1, respectively. The recoveries were in the range of 84.4–95.4%, RSD of intra-day and inter-day precision were not higher than 5.0% and 7.7%, respectively. Finally, the developed method was successfully applied for the determination of quinolones in milk.

Perspectives of Using DES-Based Systems for Solid–Liquid and Liquid–Liquid Extraction of Metals from E-Waste

In recent years, the linear economic model and global warming have shown that it is necessary to move toward a circular economic model. In this scenario, the recycling of waste electrical and electronic equipment (WEEE) with green processes is one of the pending tasks; thus, in the present review, advances in the solid–liquid and liquid–liquid extraction processes, processes among the most important for the recovery of metals from ores or WEEE, with green solvents such as deep eutectic solvents (DES) are presented and analyzed, identifying the present and future challenges. To date, most articles focused on one of the processes, be it solid–liquid or liquid–liquid extraction, while few reports included the entire hydrometallurgical process, which could be due to heterogeneity of the WEEE, a characteristic that influences determining the leaching kinetic and the leaching mechanisms. A deeper understanding of the phenomenon would help improve this process and the next stage of liquid–liquid extraction. This also leads to the fact that, at the liquid–liquid extraction stage, most articles considered synthetic pregnant leach solutions to evaluate each of the variables, whereas the stripping of the ions and the recycling of the DESs in continuous processes is a challenge that should be addressed in future work. From the analysis, for WEEE leaching, it was identified that acid DESs are those achieving the best extraction percentages in the leaching of copper, lithium, and cobalt, among others, where the most studied hydrogen bond acceptor (HBA) is choline chloride with an acid (e.g., citric or lactic acid) as the hydrogen bond donor (HBD). For the liquid–liquid extraction of ions is a greater variety of HBAs (e.g., lidocaine, trioctylphosphine oxide and triphenyl phosphate) and HBDs (e.g., decanoic acid, thenoyltrifluoroacetone, and benzoyltrifluoroacetone) used; however, studies on the extraction of cobalt, lithium, copper, and nickel stand out, where the pH and temperature parameters have great influence.

Supercritical Fluid-Assisted Fabrication of Pd Nanoparticles/Graphene Using a Choline Chloride-Oxalic Acid Deep Eutectic Solvent for Enhancing the Electrochemical Oxidation of Glycerol.

A green method for synthesizing Pd nanoparticles/graphene composites from a choline chloride–oxalic acid deep eutectic solvent (DES) without a reducing agent or a surfactant is reported. Deep eutectic solvents are usually composed of halide salts and hydrogen-bond donors, and many are biocompatible and biodegradable. The merits of deep eutectic solvents include that they serve as reducing agents and dispersants, and Pd nanoparticles are tightly anchored to graphene. The size and dispersion of Pd particles are improved when supercritical carbon dioxide (scCO2) is used because it has gaslike diffusivity and near-zero surface tension, which results in excellent wettability between the scCO2 and the carbon surface. The prepared sc-Pd NPs/GR/SPCE shows excellent activity toward glycerol oxidation compared to composites not fabricated by scCO2 processes. This study demonstrates the potential of using this scCO2-assisted protocol combined with deep eutectic solvents to further construct nanoparticles/graphene composites.

Deep Eutectic Solvents and Layered Double Hydroxides in Solid‐Phase Extraction of Antidepressant Drugs

AbstractFor the first time, an acidic deep eutectic solvent (DES) comprised of malonic acid and ChCl was used to complete dissolution of Co‐Al, Ni‐Al, and Cu‐Al layered double hydroxides (LDHs) as sorbents in the vortex‐assisted in‐situ solid‐phase extraction of doxepin and amitriptyline followed by high‐performance liquid chromatography‐ultraviolet (HPLC‐UV). Moreover, the ability of urea:ChCl and ethylene glycol:ChCl was investigated to dissolve the LDH sorbents. The extraction conditions were optimized in terms of vortex time, molar ratio of Co2+:Al3+, NaOH concentration, and volume of DES based on the Box‐Behnen design. The linearity, limit of detection, and coefficient of determination R2 for both analytes were assessed as well. Recoveries of more than 93.1 % with relative standard deviations of less than 5.3 % were achieved for spiking urine and pharmaceutical formulation samples.

Comparison of Electrochemical Polishing Treatments between Phosphoric Acid and a Deep Eutectic Solvent for High-Purity Copper

This study investigated and compared the acid-free electropolishing of copper with the state-of-the-art acidic electropolishing process. The acid-free medium used in this study is based on a deep eutectic solvent comprised of 2:1 ethylene glycol and choline chloride. The electrochemical study included voltammetry and chronoamperometry tests during the electropolishing process. The characterization techniques used were atomic force microscopy (AFM) and digital microscopy, and surface morphology comparisons summarized the electropolishing efficiency of phosphoric acid and acid-free deep eutectic solvent treatments for high-purity copper. Electropolishing copper with a deep eutectic solvent resulted in a mirror finish and a post-treatment surface that was 8× smoother than the original metal surface prior to electropolishing treatments with a smoothing efficiency of 91.1 ± 1.5%. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M H3PO4.

Combination of green solvents for efficient sugarcane bagasse fractionation

This work addresses an unprecedented combination of solvents (choline chloride and oxalic acid deep eutectic solvent, carbon dioxide, and ethanol) that were used to fractionate sugarcane bagasse into three main fractions: 1) glucan rich fibers, 2) dissolved hemicellulose sugars and co-products, and 3) precipitated lignin. To maximize the lignin removal, a two-level three-variable design of experiments assessed the effects of solids loading, DES to biomass mass ratio, and the amount of CO2. Following, kinetic were carried out in temperatures varying from 130 to 190 °C, using anhydrous and hydrated ethanol to improve hemicellulose hydrolysis and delignification. At the best condition, delignification extent as high as 90% were obtained after reaction times of 30 min. These results were accompanied by glucan contents of approximately 85 wt% and by over 80% of fibers' glucan maintenance. Also, over 60% of the hemicellulose sugars were dissolved in a liquid fraction. Finally, the third fraction was composed of the precipitated lignin with negligible carbohydrate contents. Lignin samples presented low apparent average molecular masses, and FT-IR spectra demonstrated the presence of bands typical of lignin samples from herbaceous crops. In general, this work attested to the technical feasibility of using green solvents for the efficient fractionation of sugarcane bagasse into streams that could be exploited to produce fuels, chemicals, and biomaterials.

Process optimization for acidic deep eutectic solvent pretreatment of corn stover to enhance enzymatic saccharification

Process optimization for acidic deep eutectic solvent pretreatment of corn stover to enhance enzymatic saccharification

Toward reactive extraction processes for synthesizing long-chain esters: A general approach by tuning bifunctional deep eutectic solvent

The synthesis of long-chain esters in reactive extraction using bifunctional deep eutectic solvent (DES) demands a wide solvent selection range and optimal solvent choice. In this work, a general approach towards rational DES selection is presented. First, novel halogen-free DESs based on triazole and p-toluenesulfonic acid (PTSA) or benzenesulfonic acid (BSA) are prepared to expand the selection range of Brønsted acidic DESs, whose binary solid–liquid phase diagrams are measured to confirm the DES formation. Then, the triazole-PTSA/BSA DESs together with the imidazole (Im)-PTSA/BSA DESs are characterized by pH measurement, 1H-NMR characterization, and COSMO-RS interaction energy analysis, which reflect a two-step formation mechanism. The Im-PTSA/BSA DESs are acid-base tunable while the triazole-PTSA/BSA DESs are tunable from weak acid to strong acid. Afterwards, four strong acidic DESs at the eutectic compositions namely [Im:2BSA], [Im:2PTSA], [triazole:4BSA] and [triazole:4PTSA] are determined as dual solvent-catalyst for the intensified esterification with ester carbon chain length changing from C6 to C11. Combining σ-potential thermodynamic analysis with experimental results, the applicable boundary and change rule of carbon chain length versus different DESs are clarified. On this basis, a rational DES selection strategy is formulated aiming to the development of reactive extraction for synthesizing different long-chain esters.

Oriented Deep Eutectic Solvents as Efficient Approach for Selective Extraction of Bioactive Saponins from Husks of Xanthoceras sorbifolia Bunge

The husks of Xanthoceras sorbifolia Bunge (X. sorbifolia), as by-products of industrial production, have brought a severe burden to the environment and caused an enormous waste of resources. Bioactive triterpenoid saponins are rich in the husks. To reuse the husks and gain high-quality saponin products, saponin-oriented deep eutectic solvents (DESs), as an efficient and selective extraction strategy from X. sorbifolia husks, were designed for the first time. The enhancement of the extraction rate was investigated by screening solvents from acidic DESs and response surface methodology (RSM) optimization. As a result, the tetrapropylammonium bromide-lactic acid (TPMBr-La) was the most efficient DESs, with an extraction efficiency of up to 135% higher than 70% ethanol. A maximum extraction rate of 72.11 ± 0.61 mg Re/g dw was obtained under the optimized parameters. Scanning electron microscope graphs revealed that damage to the microstructure caused by DESs enhanced the extraction efficiency. Moreover, the recovery of total saponins with D101 macroporous resin was consistent with the pseudo-second-order kinetic model. Seven saponins were also identified by HPLC-MS analysis. Finally, TPMBr-La extracts exhibited 92.30 ± 1.10% DPPH radical scavenging rate at 100 μg/mL, and 92.20 ± 0.30% ABTS radical scavenging rate at 1200 μg/mL. Our current research proposes a selective and high-efficiency substitute for the extraction of saponins and might contribute to further DESs application in the recycling of by-products.

Solvent-free synthesis of oleic acid-based wax esters using recyclable acidic deep eutectic solvent

Wax esters have been widely used in cosmetics and pharmaceutical products. Oleic acid wax esters can be used to replace spermaceti oil or jojoba oil. In this work, the acidic deep eutectic solvent (DES) composed of choline chloride and p-toluenesulfonic acid (1:4, mol/mol) was used as an efficient recyclable catalyst for the synthesis of oleic acid-based liquid wax esters through an esterification reaction. The esterification conversion of cetyl alcohol reached 99.1% under the following optimal reaction conditions: 5% DES as catalyst, molar ratio of fatty acid to alcohol of 1.3:1 and reaction temperature of 70 oC for 3h. The catalyst recovery experiments showed that this low-price acidic DES catalyst could be reused five times with uniform activity. Moreover, DES-catalyzed solvent-free esterification could be applied in the preparation of other oleic acid-based wax esters and excellent conversions (> 96%) could be obtained under such mild conditions.

New and efficient magnetic nanocomposite extraction using multifunctional deep eutectic solvent based on ferrofluid and vortex assisted-liquid–liquid microextraction: Determining primary aromatic amines (PAAs) in tetra-packed fruit juices

In this work, a novel magnetic nanocomposite solvent (MNCS) based on ferrofluid and multifunctional deep eutectic solvent (MDES) was synthesized and applied in vortex assisted-liquid–liquid microextraction (VA-LLME). The ferrofluid has been composed from zirconium phosphate (modified magnetic graphene oxide) and tetrabutylammonium bromide-octanoic acid deep eutectic solvent (MGO/α-ZrP@TBAB-OA). This efficient method was employed to determine primary aromatic amines including aniline, 4-methoxyanniline, 4,4′-diaminodiphenylmethane, orthotoluidine, 2,6-dimethylaniline, 2-naphtylamine in tetra-packed juice samples. The proposed method showed the excellent extraction efficiency of PAAs according to strong interactions of new extraction solvent including electrostatic, π-π, and hydrogen bonding attractions. The found levels of PAAs are lower than the limit of quantifications (2.0 µg L−1). Therefore, the migration of PAAs from packaging to the juice samples is lower than permitted level (<10 µg kg−1). The results indicated high potential use of the offered method to analyze aromatic amine compounds in foodstuff and biologic samples in the future.

Investigation into Lewis and Brønsted acid interactions between metal chloride and aqueous choline chloride-oxalic acid for enhanced furfural production from lignocellulosic biomass

Furfural has been identified as a valuable biobased platform chemical that can be further converted into bioenergy and biochemicals. Furfural is derived from lignocellulosic biomass and can also be regarded as a sustainable alternative to petrochemical products. Herein, the performance of trivalent metal chlorides (FeCl3, AlCl3) and tetravalent metal chlorides (SnCl4, TeCl4) as Lewis acidic cocatalysts was investigated in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent (DES) system for producing furfural from oil palm fronds (OPFs). The metal chlorides with greater electrical field gradients were stronger Lewis acids that enhanced both furfural production and degradation reactions. The main degradation product in this reaction system was humin, and this result was confirmed by FTIR analysis. By subjecting OPFs to an aqueous DES reaction (120 °C, 45 min) with SnCl4 (2.50 wt%), a furfural yield of 59.4% was obtained; without incorporated metal chlorides, the furfural yield was 46.1%. Characterization studies showed synergistic Lewis and Brønsted acid interactions between metal chlorides and DES components. Overall, the residual OPFs showed high glucan content, which led to the production of glucose (71.4%) as a byproduct via enzymatic hydrolysis. Additionally, the aqueous DES system was recycled and reused for several additional runs. The proposed aqueous DES system presents a promising biorefinery approach for the conversion of OPFs to biochemicals.

Preparation strategy and stability of deep eutectic solvents: A case study based on choline chloride-carboxylic acid

Deep eutectic solvents (DESs) with designable physicochemical properties are expected to be successfully used in wide fields. Different preparation methods for DESs based on various feedstocks could result in different expectations. In this study, we focused on the preparation strategy for choline chloride-carboxylic acid to get homogeneous liquid DESs and to understand the effects of some process parameters on the formation and the impurities of DESs. For the preparation of DESs, heating is more suitable for liquid acids, while freeze-drying is more suitable for DESs with thermally unstable components. For the hydrogen bond donor (HBD) with more carboxyl or hydroxyl groups, freeze-drying or rotary evaporation are more suitable. The impurities in DESs are different from various preparation methods due to the different process conditions. Besides, the molecular interactions of choline chloride-carboxylic acid DESs were measured by FT-IR spectroscopy and analyzed with the aid of density functional theory (DFT) calculations. Our results provide the underlying insights to guide the selection of preparation methods for DESs with different structures.

Improved Production of 5-Hydroxymethylfurfural in Acidic Deep Eutectic Solvents Using Microwave-Assisted Reactions.

Hydroxymethylfurfural (5-HMF) is a key platform chemical, essential for the production of other chemicals, as well as fuels. Despite its importance, the production methods applied so far still lack in sustainability. In this work, acidic deep eutectic solvents (DES), acting both as solvent and catalyst, were studied for the conversion of fructose into 5-HMF using microwave-assisted reactions. These solvents were screened and optimized by varying the hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA). The bio-based solvent γ-valerolactone (GVL) was also applied as additive, leading to a boost in 5-HMF yield. Then, a response surface methodology was applied to further optimize operating conditions, such as reaction time, temperature and wt.% of added GVL. The highest 5-HMF yield attained, after optimization, was 82.4% at 130 °C, in 4 min of reaction time and with the addition of 10 wt.% of GVL. Moreover, a process for 5-HMF recovery and DES reuse was developed through the use of the bio-based solvent 2-methyltetrahydrofuran (2-Me-THF), allowing at least three cycles of 5-HMF production with minimal yield losses, while maintaining the purity of the isolated 5-HMF and the efficacy of the reaction media.

Development of dispersive solid-liquid extraction method based on organic polymers followed by deep eutectic solvents elution; application in extraction of some pesticides from milk samples prior to their determination by HPLC-MS/MS

An effective extraction procedure based dispersive solid phase extraction was developed for the extraction of different pesticides (dimethoate, imidacloprid, pirimicarb, carbaryl, fenitrothion, hexythiazox, and phosalone) from milk samples. The analytes were determined by high performance liquid chromatography-tandem mass spectrometry. In this method, an organic polymer (polystyrene) was dissolved in a water-miscible organic solvent (tetrahydrofuran) and it was injected into the aqueous phase obtained from milk sample after deprotonation. By this action the sorbent (polymer) was precipitated and dispersed in the solution as tiny particles. By doing so, the pesticides were adsorbed onto the sorbent. After that, the sorbent was separated by centrifugation and the adsorbed analytes were eluted by tetrabutylammonium chloride: dichloroacetic acid deep eutectic solvent. After optimization, the method validation was followed according to Food and Drug Administration and International Research Council guidelines and the results showed that wide linear ranges (0.93–500 ng/mL) and low limits of detection (0.09–0.27 ng/mL) and quantification (0.31–0.93 ng/mL) were obtained. Extraction recoveries and extraction and enrichment factors were in the ranges of 81–94% and 162–188, respectively. Relative standard deviations were less than 9% for intra– (n = 6) and inter–day (n = 6) precisions at three concentration of 2, 5, and 25 ng mL−1 of each analyte. The developed method was successfully applied to twenty cow milk samples for determination of the pesticides.

Efficient removal of trace olefins in aromatics by novel acetamide-based acidic deep eutectic solvents

The alkylation of olefins with aromatics (AOA) is considered an attractive method for removing trace olefins from aromatics. The catalyst with appropriate acidity is an important feature to control the alkylation reaction. In this work, a series of innovative acetamide (AC)-based acidic deep eutectic solvents (ADESs) with different organic sulfonic acids as hydrogen-bond donors (HBDs) were synthesized and used in AOA. The formation mechanism of ADES was investigated utilizing FT-IR spectroscopy, 1H NMR, and quantum chemistry calculations combined with the phase diagram. In addition, the factors affecting the removal of olefins were further studied. Under optimal conditions, the most effective ADES ([AC:2TfOH]) can achieve 100% olefin conversion, and it can still reach 90% after 8 cycles. Finally, the mechanism of ADES ([AC:2TfOH]) catalyzed alkylation of aromatics and olefins was first investigated and proposed by in-situ diffuse reflectance infrared spectroscopy (in-situ DRIFT) and gas chromatography-mass spectrometry (GC–MS).

Development of a gas–controlled deep eutectic solvent–based evaporation–assisted dispersive liquid–liquid microextraction approach for the extraction of pyrethroid pesticides from fruit juices

In current study, a new mode of evaporation–assisted dispersive liquid–liquid microextraction method named as gas–controlled–deep eutectic solvent–based evaporation–assisted dispersive liquid–liquid microextraction has been proposed for the extraction of pyrethroid pesticides from fruit juices prior to their quantification by gas chromatography–mass spectrometry. In the proposed approach, a mixture of choline chloride: butyric acid deep eutectic solvent (as an extractant) and chloroform (as a density modifier) is added to aqueous solution of the analytes placed into a narrow–bore tube. Afterward nitrogen gas is bubbled into the tube through a glass syringe barrel connected to a needle. By this action, chloroform is evaporated and removed from the system and tiny droplets of the extractant are released. The droplets move up through the aqueous phase owing to their low density in comparison with the aqueous phase and the analytes are extracted into them. Several factors which can affect capability of the method were explored. Under final conditions, extraction recoveries and enrichment factors were attained in the ranges of 83–92% and 623–690, respectively. Relative standard deviation at a concentration of 150 ng L–1 (each analyte) was less than 6.9%. Limits of detection and quantification were in the ranges of 9–21 and 31–69 ng L–1, respectively. At the end, the offered approach was done on various fruit juice samples marketed in Tabriz city (Iran) and based on the outcomes the studied samples were free of the selected pesticides.